1. Field of the Invention
The invention relates to an auto-focus device and a method for controlling operation of the same.
2. Description of the Related Art
Examples of auto-focus modes of a camera include phase difference AF (auto-focus) and contrast AF. In the phase difference AF, light incident from a lens is divided into two or three or more rays through a pupil division, and is guided into a phase difference AF sensor, and a focusing direction and an amount of defocus are determined on the basis of an amount of position shift or a position shift direction of directions of division of the images divided through the pupil division. In the contrast AF, by locating a high contrast portion while moving a focus lens on the basis of an image captured by an imaging element, a focus is adjusted thereto. In a television camera, an image of a subject is captured by two imaging elements which are disposed at positions where optical path lengths are different from each other, and the contrast AF (optical path length difference AF) for adjusting a focus on the basis of the image signals obtained from respective imaging elements is used. The contrast AF is characterized in that accuracy in focusing is high while a focusing speed is low. The phase difference AF is characterized in that the focusing speed is high while the accuracy in focusing is low. Thus, in order to compensate for respective defects, a system having both the contrast AF and the phase difference AF may be used. Further, as a system having both the contrast AF and the phase difference AF, there is a system in which a width of WOB for finding the focusing direction by moving the focus lens by a small distance is increased when a detection area of the phase difference AF and a detection area of the contrast AF do not coincide with each other (JP4946311B). Alternatively, there is also a system in which a focusing evaluation value of the contrast AF is used when the detection area of the phase difference AF and the detection area of the contrast AF coincide with each other and the focusing evaluation value of the contrast AF is greater than the threshold value (JP4962021B).